The percentage of the economically active population is an important index of development. Occupational structure refers to the distribution of the population according to different types of occupation. Various types of occupations are found in any country. Occupations are, generally, classified as primary, secondary and tertiary. Primary activities include agriculture, animal husbandry, forestry, fishing, mining and quarrying, etc. Secondary activities include manufacturing industry, building and construction work, etc. Tertiary activities include transport, communications, commerce, administration and other services.

The number and percentage of people working in different activities depend upon the developed and developing countries. Developed nations have a high proportion of people in secondary, and tertiary activities while developing nations have a high proportion of people involved in primary activities. In recent times, there has been an occupational shift in favour of secondary and tertiary sectors because of growing industrialisation and urbanisation.